Chronic Myelogenous Leukemia Classification

William Dameshek in 1951 first described the term chronic myeloproliferative disorder. It encompassed four entities that were clinically separate. These included:

Chronic myelogenous or myeloid leukemia (CML)

Polycythemia Vera (PV)

Essential Thrombocytosis (ET)

Chronic Idiopathic Myelofibrosis (CIMF)

It was in 2001 that the World Health Organization added several entities to this list including:

Chronic Neutrophilic Leukemia (CNL)

Chronic Eosinophilic Leukemia (CEL)

CEL/Hypereosinophilic Syndrome

Chronic Myeloproliferative Disorder, Unclassified

This list was further modified in 2008 by the WHO. The WHO then changed the terminology from “myeloproliferative disease” to “myeloproliferative neoplasm”. In addition they added Mastocytosis to this new category.

The diagnostic criteria were also altered from the 2001 report. The new categories included:

Myeloproliferative Neoplasms (MPN)

CML, BCR-ABL1 positive

Chronic Neutrophilic Leukemia CNL

Polycythemia Vera (PV)

Primary Myelofibrosis (formerly CIMF)

Essential Thrombocytosis ET

Chronic Eosinophilic Leukemia CEL, Not Otherwise Specified (NOS)

Mastocytosis

Cutaneous Mastocytosis

Systemic Mastocytosis

Mast Cell Leukemia

Mast Cell Sarcoma

Extracutaneous Mastocytoma

Myeloproliferative Neoplasms MPN, Unclassifiable

Myeloid and lymphoid neoplasms associated with eosinophilia and abnormalities of PDGFRA, PDGRRB or FGFR1

For clinical diagnosis

In CML the White blood cell (WBC) count usually is around 100,000, with absolute basophilia, and <2% myeloblasts; with variable hemoglobin and platelet levels

In Polycythemia Vera hemoglobin usually 19-20 gm/dL and WBC count usually less than 20-30,000, and normal to slightly elevated platelet count

In Essential Thrombocytosis platelet count usually more 1,000,000 WBC count usually less than 20-30,000, and normal to low hemoglobin level

Bone marrow examination:

In CML there is granulocytic hyperplasia. Cells are absent-to-minimal in early (Chronic Phase) disease and are increased in late stages.

In PV there is erythroid hyperplasia or excessive growth of the RBC precursors. Cells are absent-to-minimal in early disease and are increased in late stages.

In ET megakaryocytic hyperplasia or excessive growth of the platelet precursors.

In MPN there is fibrosis

In mastocytosis there are mast cell infiltrates. The cells form loosely scattered nest like formations

Cytogenetic analysis:

In CML 90-95% of cases will have the characteristic translocation at chromosomes 9 and 22 called the Philadelphia Chromosome t(9:22). -10% of cases will have a variant translocation or a cryptic translocation of 9 and 22.

In PV more than 95% of patients with have a point mutation in the Janus Kinase2 gene (JAK2)—V617F or at JAK2 exon 12 mutations. JAK2 kinase is a member of a family of tyrosine kinases.

In ET 40-50% of patients have the JAK2 V617F mutation. 1% will have a mutation in MPL—MPL W515K/L

In Mastocytosis more than 95% will have a mutation at the D816V, within the KIT tyrosine kinase gene.

Ananya is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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